The main function of the nervous system is to process information in ways that lead to adaptive behavior, and to accomplish this, the excitability of neurons and the strength of their synaptic connections need to be modulated continually. After a neuron or neural system has been analyzed extensively, it becomes possible to ask what information it carries and how it contributes to this plasticity. At this point, there is generally so much data that only computational approaches can explain how individual components of a system interact, however. This Program Project will apply constructionistic computational techniques to several such well- characterized neural systems to achieve a more complete understanding of neuronal information processing and plasticity. The Project will examine multiple levels of organization, ranging from genetic networks within neurons to neural circuit. The individual projects will examine: 1) the dynamic properties and interactions of gene networks and excitable membranes; 2) the contribution of plasticity in individual neurons to associative learning; 3) the computational role of cellular and synaptic plasticity in an oscillatory neural circuit; and 4) the role of dopamine in light and dark adaptation in the primate retina. The individual projects are linked by a common goal of investigating plasticity in neurons and determining its contributions to higher levels of processing. For example, simulation of simple forms of cellular and synaptic plasticity may provide insights into the roles of these distinct mechanisms in the information processing capabilities of larger-scale neural networks such as those controlling feeding behavior. The group will be supported by a Computational Core that serves as a resource for developing models and for the exchange of information among the project groups. Another important goal of the project is to train graduate students and postdoctoral fellows in Computational Neuroscience. Finally, the Projects will further develop general-purpose simulation programs for neuronal and biochemical modeling, which will be used by the Program Project group. These programs will also be widely distributed to other groups who wish to apply computational approaches to analyze the properties of nerve cells and neuronal networks.